The possibility of long term cerebral damage from the blows that occur in boxing has been a source of considerable controversy for years and may be relevant to the broader issues of head injuries. In many ways, the injuries that occur in amateur boxing, a sport vastly different from professional boxing, are more analogous to those that occur in other sports and accidents. Therefore, a study of whether cerebral damage occurs in amateur boxing would have both specific and broad epidemiologic and medical implications. We have begun and will shortly complete the first phase of a study of 500 amateur boxers designed to answer the question of whether selected neuropsychologic, neurologic, or neurophysiologic changes which occur after a 2-year interval are associated with varying degrees of exposure ranging from essentially none to repeated subconcussive and in some cases, concussive blows. This study is unique in that boxers are identified before any apparent signs of impairment, it is prospective, and involves a representative sample of 500 subjects. In addition, a low dose internal control is used. Our preliminary studies have shown that boxers appear to have enough unique characteristics that other plausible control populations are probably not appropriate. This study design was developed in concert with an external advisory committee comprised of neuropsychologists, an epidemiologist, neurologist, neurosurgeon, biostatistican, boxing coach, and other authorities. This proposal is to request funds for the follow-up measures (after a two year interval) on these same boxers. In the soon to be completed baseline study neuropsychologic, electrophysiologic, and neurologic measures are made in a 4-hour test session. All tests are completed in a mobile clinic. Urine samples are collected to test for recent substance use. A detailed boxing history is obtained from the boxer and coach. The proposed follow-up measures will be made using the baseline study protocol. Follow-up measures are proposed after a 2-year interval, as a compromise between a desire to maintain close contact with subjects and a meaningful interval long enough to observe changes. Interim contact is being maintained with subjects to assure a high follow-up rate in the event that prospective measures are to be made.